JPH0544047A - Method for electroless plating - Google Patents

Abstract

PURPOSE:To realize simplification of pretreatment process, reduction in cost, and simplification of waste water treatment of an electroless plating method. CONSTITUTION:A material to be plated is treated at the temp. as high as about >=80 deg.C with a soln. containing a tervalent iron ion and bivalent metal ions which can form a ferrite magnetic material with the iron ion. Then the material is neutralized to precipitate the ferrite and then treated in an electroless plating bath. Thus, the man-hour and the cost can largely be reduced. Advantages are that low-purity water can be used, the waste water treatment is simplified, the plating time is short owing to high temp. treatment, and that the obtd. plating film has high strength and large shielding effect against electromagnetic waves.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention performs a ferritic treatment instead of a sensitizing treatment and an activating treatment when electrolessly plating a molded body or powder of synthetic fiber, plastic, glass fiber, ceramics or the like. Accordingly, the present invention relates to a novel electroless plating method which can omit steps to obtain plating with excellent stability.

[0002]

2. Description of the Related Art Electroless plating is a method of plating by simply immersing an object to be plated in a plating bath.

The features of electroless plating are: (1) It is possible to plate non-conductors such as plastics and ceramics other than metals by performing sensitizing treatment and activating treatment as pretreatment, and (2) complicated Even an object with a different shape can be plated with a uniform thickness, (3) a plated film with fewer pinholes can be obtained, and a film with better corrosion resistance than electroplating can be obtained. (4) Unique functionality (magnetic, non-magnetic) A plating film with crystallinity is also possible, (5) Equipment,
On the other hand, there is an advantage that the operation is simple, but on the other hand, the pretreatment is complicated and the cost is higher than that of the electroplating.

In the conventional electroless plating method, the composition of the pretreatment process is not constant depending on the material of the material to be plated, but when plating plastics or the like, usually an alkaline solution (NaOH) is used.
_{20~30g / l, Na 2 CO 3} 20~30g /
1, Na ₃ PO ₄ 20 to ₃₀ g / l, a surfactant) or a degreasing step of immersing in an organic solvent, xylene, dioxane, toluene, tetralin, dimethylformamide,
A solvent treatment process using an organic solvent such as dimethyl sulfoxide or tetrahydrofuran, a CrO ₃ —H ₂ SO ₄ —H ₂ O solution (Cr
O ₃ 100~500g / l) or this H ₃ PO ₄
Etching step of immersing in a solution with added at high temperature, then SnCl ₂ · 2H ₂ O 5 to 40 g / l, HCl ^conc
A sensitizing step of immersing in a sensitizing treatment solution of 1 to 10 g / l to adsorb Sn ^2+, and an activation of precipitating Pd ⁰ on the surface of the material to be plated by the reaction of reducing Pd ²⁺ by this Sn ²⁺ The pretreatment process of the electroless plating process is completed through the steps.

In this case, the sensitizing step and the activating step are immersed in the sensitizing treatment solution and the activating treatment solution at a low temperature of room temperature (around 20 ° C.) for 1 to 2 minutes. Washing with a large amount of water is required before moving to the process. In particular, the sensitizing step and the activating step are rarely required to be performed only once in order to completely apply plating, and usually, a plurality of repeated treatments are performed.

Then, the material to be plated which has been subjected to such a pretreatment is usually plated by a dipping method in a plating bath composed of a metal salt containing a metal to be plated, a complexing agent and a reducing agent. Noble metals such as nickel, copper, cobalt and gold, silver and indium are mainly used as the plating metal.

As described above, the pretreatment of the electroless plating method includes a degreasing step, a solvent treatment step, an etching step,
In addition to many steps such as sensitizing step and activating step, washing step and solvent recovering step between each step, and sensitizing step and activating step require multiple repeated treatments. There have been problems such as an extremely large number of steps and the need for expensive palladium salt as a treating agent.

[0008]

DISCLOSURE OF THE INVENTION The present invention has been studied for the purpose of simplification of steps, cost reduction and simplification of wastewater treatment, which are unsolved problems of the pretreatment step of the conventional electroless plating method, The present invention has been reached.

[0009]

According to the present invention, a material to be plated is treated with a solution containing trivalent iron ions and a divalent metal ion capable of forming a ferrite magnetic material and neutralized,
After depositing ferrite on its surface or internal surface,
The above object was achieved by developing an electroless plating method characterized by treatment in an electroless plating bath.

There is no reason to limit the material of the material to be plated which is the subject of the present invention, as long as it is not attacked by the pretreatment liquid and the electroless plating bath used in the present invention. In addition, the shape is also a method that can be used even for an object having a complicated shape, which is a feature of the electroless plating method.
It is also applicable to woven fabrics of inorganic fibers such as glass fibers, synthetic fibers, organic fibers such as natural fibers, textile products such as nonwoven fabrics and filaments, shaped products such as glass, ceramics, plastics, and powders.

The pretreatment liquid is a solution containing trivalent iron ions and divalent metal ions capable of forming a ferrite magnetic material with the iron ions. The trivalent iron ion is preferably a salt of a strong inorganic acid such as ferric chloride or ferric sulfate. When using ferrous ions as the divalent metal, it is preferable to avoid the use of highly oxidizing nitrates. Further, as divalent metal ions capable of forming a ferrite magnetic material with trivalent iron ions, there are iron, nickel, cobalt, copper, manganese, etc., but considering the price and the ease of handling including wastewater treatment, etc. Iron ions are preferred. And it is preferable that both are common anions, and the combination of ferric chloride-ferrous chloride is the most preferable combination. The concentration in this case is 1 to 300 g / l as ferric chloride, preferably 5 to 100
g / l. If the concentration is lower than 1 g / l, the amount of ferrite deposited is small, which requires multiple treatments, and even if electroless plating is performed as it is, complete plating is impossible and there is a risk of mottle. Further, even if the concentration is higher than 300 g / l, the corrosiveness of the pretreatment bath only becomes high and the effect is not particularly improved. Ferrous ions are convenient for forming ferrite in an amount of about 0.2 to 5 mol with respect to 1 mol of ferric ions.

The material to be plated is dipped in this pretreatment liquid. The time and temperature depend on the material and shape of the material to be plated,
Although it cannot be generally stated because it is affected by the concentration of ferric-divalent metal ions in the pretreatment liquid, the treatment temperature is 80 ° C or higher (if the material is glass, carbon, ceramics, etc., high pressure should be 100 ° C or higher. The above treatment is also possible), but the treatment is usually performed for about 10 minutes.

When the treatment with the above-mentioned pretreatment liquid is completed, it is simply washed with water (for glass, ceramics, plastics, etc., centrifugation or drying is also possible). If the pretreatment liquid is a ferric-ferrous system, the oxide system produced is stable even if it is heat-treated, and even if it is washed with water, the wastewater treatment can be simple.

Next, the material to be plated, which has been treated with the pretreatment liquid, is neutralized with ammonia water, an aqueous alkali solution, ammonia gas or the like. Organic substances such as ammonium chloride cannot be subjected to a high-temperature treatment such as volatilization or sublimation of ammonium salts, and therefore, it is convenient to neutralize with an aqueous solution and simultaneously wash the formed salts with water. In particular, ammonia water is excellent in that even if it is used excessively, it is only dried and does not remain. By this neutralization, ferric ions and divalent metal ions become hydroxides and are fixed to the material to be plated.

The material to be plated on which the metal hydroxide is fixed is then dehydrated. 12 depending on the material
Heat to 0 ° C or higher (200 to 300 ° C or higher if the material permits). Depending on the type of plastic, it is unavoidable that the temperature is 120 ° C or lower, but dehydration and ferritization are performed at a high temperature that the material allows (this is referred to as ferrite in the present invention because it has an effect even if it is not sufficiently ferrite. Yes.)

When the material to be plated is such as glass, fiber, carbon fiber, etc., which can withstand a considerable high temperature, it is treated with a pretreatment liquid, and then the liquid is cut off and treated with ammonia gas at a high temperature to salinize. Ammon can be removed and the metal hydroxide can be converted to ferrite.

The material to be plated, which has been subjected to the pretreatment process as described above, is sent to the electroless plating process, and various metals such as A are used.
Metal plating of u, Ag, Pd, Cu, Ni, Co, Fe, Ir or the like is performed. The product pretreated by the electroless plating method of the present invention can be subjected to electroless plating in the same electroless plating bath as the product pretreated by the conventional method.

[0018]

The pretreatment step of the electroless plating method according to the present invention includes a degreasing step, a bath agent treatment step, an etching step, a sensitization treatment step, and an activation treatment step before including one stage of ferric iron and divalent metal ions. The treatment liquid is used and replaced by treatment at high temperature.

Particularly, the sensitization treatment step with stannous chloride and the activation treatment step with palladium chloride, which are usually performed a plurality of times, which have been regarded as indispensable steps in the conventional pretreatment step, are completely omitted. The fact that the pre-treatment for conversion into a finished product is a great force for simplifying the process.

Further, although the reason has not been clarified, in the case of the pretreatment of the present invention, water having a purity as high as tap water is sufficient instead of pure water, and the plating rate of the electroless plating method is increased. In addition to being able to obtain a product in which the adhesion strength of the plating film is high, it also has the advantage that the residual amount of metal ions in the liquid after plating can be kept low.

[0021]

EXAMPLES The present invention will be described more specifically below with reference to examples. (Example 1) The weight ratio of ferrous chloride to ferric chloride is 1: 3.
˜3: 1 mixture of 5.0 g / l and 20 g / l of 2
Using a pretreatment liquid having a concentration of seeds, an acrylic short fiber having a thickness of 2 denier and a length of 5 mm was used in an amount of 50 per 1 liter of the pretreatment liquid.
Immersion treatment was performed for 10 minutes at two points of treatment temperature of 95 ° C. and 80 ° C. Then, after immersing in a 1% aqueous ammonia solution, it was dried at 120 ° C. and made into a ferrite to be a pretreatment.
Nickel sulfate hexahydrate 30 g / l, ammonium chloride 50
p consisting of g / l and sodium hypophosphite 10 g / l
The electroless plating bath of H8 to 10 was treated at a temperature of about 90 ° C. for 10 minutes, and the plating state was visually observed. For comparison, as experiment number 8, alkali degreasing, solvent treatment, and chromic acid-used in ordinary electroless plating pretreatment
The same acrylic short fibers as described above, which had been subjected to etching treatment with sulfuric acid, sensitization treatment with stannous chloride 5 g / l solution, and activation treatment with palladium chloride 0.1 g / l solution, were used. Further, Experiment No. 9 shows the case where the pretreatment liquid used in the examples was ferrous chloride 5.0 g / l, and Experiment No. 10 shows the case where ferric chloride 5.0 g / l was used as the pretreatment liquid. It was The results are shown in Table 1.

[0022]

(Example 2) Using the metallized fibers of Example 1, a nonwoven fabric was produced by a papermaking method, and this was hot pressed into a sheet, which was tested for shielding against electromagnetic waves. Polyvinyl alcohol 1 as a papermaking method
g, 10 g of the plated fiber obtained in Example 1 was mixed with 1 liter of water to prepare a papermaking liquid, and
mm, and a non-woven fabric having a basis weight of 100 g / m ² . Then, after dewatering with a low pressure press (10 Kg / cm ² ), 40 Kg / c
It was formed into a sheet by a high-pressure hot press at m ² , 80 ° C. and 100 Kg / cm ² , 80 ° C. This sheet was subjected to a test of electromagnetic wave shielding property and a dirt adhesion state (electrostatic generating property) using a TR4131 electromagnetic shielding test device manufactured by Advantest. The degree of adhesion of dirt is 20 ° C, 1
The sample was left in a thermo-hygrostat of 0% RH for 1 month, and the results were observed. In the evaluation column, ○ means no dust adherence, × means large dust adherence amount, and Δ means intermediate. Regarding the electromagnetic wave shielding property, the experiment numbers a to h are the case where the sample metallized fiber molded product is wrapped with a metal copper foil and set in the conductive state of the measuring device, and the experiment numbers i to j are the sample metallized fiber molded product and the polypropylene film. It was measured in a state wrapped in. The results are shown in Table 2.

[0024]

[0025]

The pretreatment step of treating the material to be plated with a solution containing the trivalent iron ion of the present invention and the divalent metal ion capable of forming the ferrite magnetic substance and precipitating the ferrite on the surface thereof is adopted. According to the electroless plating method described above, (1) the number of steps was significantly reduced compared to the pretreatment of the conventional electroless plating method, and the number of washings was also reduced, so the amount of drainage was reduced. (2) Whereas the water for the conventional plating step requires pure water, the method of the present invention can be used with a purity as high as tap water. (3) In the conventional method, it was necessary to use tin and palladium compounds for pretreatment (sensitizing treatment and activating treatment), but in the present invention, pretreatment is possible with only an inexpensive iron compound. (4) Since only the iron compound can be used in the pretreatment process, wastewater treatment in the process can be simplified and the cost can be reduced. (5) Since the electroless plating method of the method of the present invention is at a high temperature, the plating rate is fast. (6) The adhesion strength of the plating film is high. (7) The metal plating film of the present invention has a large electromagnetic wave shielding effect. It is a very excellent plating method.

Claims (6)

[Claims] 1. A material to be plated is treated with a solution containing trivalent iron ions and a divalent metal ion capable of forming a ferrite magnetic material, neutralized, and ferrite is deposited on the surface of the plated material. An electroless plating method characterized by treatment in an electrolytic plating bath. 2. The electroless plating method according to claim 1, wherein iron, nickel, cobalt, copper and manganese are used as the divalent metal ions forming the ferrite magnetic material with the trivalent iron ions. 3. After neutralization, the material to be plated with the ferrite precursor deposited on the surface is heated to 80 ° C. or higher or left in vacuum and then electroless plated. The described electroless plating method. 4. The electroless plating method according to claim 1, wherein the material to be plated is a fiber, a molded product, or a powder. 5. The electroless plating bath is nickel, nickel-
The electroless plating method according to claim 1, which is a plating bath for phosphorus, cobalt-phosphorus, nickel-cobalt, and nickel-iron. 6. An electromagnetic wave shielding material comprising a material to be plated, which is metal-plated by the method of claim 1.